This invention relates to the field of subsurface well apparatus and method for using same.
Subsurface safety valves are sometimes employed as catastrophic protection systems in wells for controlling flow of well fluids from the well producing formation at a subsurface location below the well head to avert well flow under disaster conditions or failure of the surface flow control systems. Operation of such subsurface safety valves may either be controlled by the well conditions--differential or ambient pressure--directly sensed by the valve at the subsurface location (direct-controlled) or controlled from the surface by a suitable control means (remote or surface-controlled). For a more detailed consideration of these types or categories of down hole or subsurface safety valves see the article entitled "Platform Safety by Down Hole Well Control" which appeared in the March 1972 issue of the Journal of Petroleum Technology published by the Society of Petroleum Engineers, Dallas, Tex.
Early examples of rotatable ball-type surface controlled subsurface safety valves include Knox U.S. Pat. No. 3,035,808, Fredd U.S. Pat. No. Re. 25,471 and Bostock U.S. Pat. No. 2,998,070. While these patents disclose the use of a rotatable ball-type flow closure element, other types of flow closure elements such as a flapper element as disclosed in Natho U.S. Pat. No. Re. 25,109 are also known. In general, these early surface-controlled subsurface safety valves were of the tubing retrievable type in that the upper and lower ends of the tubular valve housing were provided with means, normally threads, for connecting the valve housing in the production tubing and making the valve retrievable with the tubing, hence the designation of this type of valve as tubing retrievable. With a tubing retrievable type valve it is necessary to remove or pull the production tubing from the well in order to replace or repair the leaking or damaged valve and such tubing removal and installation operations are both expensive and hazardous and may result in permanent damage to the producing formation.
In order to overcome this problem with tubing retrievable valves, surface controlled wireline retrievable valves were developed such as disclosed in U.S. Pat. No. Re. 26,149 and U.S. Pat. No. 3,667,505. In general, these through-the-bore movable or wireline retrievable valves severely restricted the flow area through the valve due to the manner of their operation which required pressure responsive surfaces for the control fluid to be carried by the wireline retrievable valve.
Some attempts to overcome the disadvantages found in the prior art have used a combination of a surface-controlled tubing retrievable valve receiving and operating a wireline retrievable valve with the controls of the tubing retrieval when the tubing retrievable valve fails. U.S. Pat. No. 2,998,077 discloses the concept of locking a tubing retrievable valve open to conduct well operations through the valve while Canadian Pat. No. 955,915 and corresponding U.S. patent application Ser. No. 72,034, now abandoned, after filing continuation application Ser. No. 256,194 discloses the concept of releasably locking the tubing retrievable valve open. Such an arrangement is also disclosed in U.S. Pat. Nos. 3,696,868 and 3,868,995.
Mott U.S. Pat. No. 3,763,933 discloses the combination of a tubing retrievable valve and a wireline retrievable valve in which the wireline retrievable valve is operated off the controls of the tubing retrievable valve without the tubing retrievable valve being locked open.
Mott U.S. Pat. No. 3,762,471 also discloses a tubing retrievable valve that is locked open and the wireline retrievable valve operated off the controls of the tubing retrievable valve. That patent further disclosed the use of a movable landing ring for operably positioning the wireline retrievable valve in the tubing retrievable valve for releasably securing.
Mott U.S. Pat. No. 3,744,564 disclosed an improved wireline retrievable or drop-in valve in which the drop-in valve operator sleeve was secured with the reciprocating tubing operator of the tubing retrievable valve to assure positive operation of the wireline valve. The wireline retrievable valve disclosed in these three Mott patents considered immediately above and their divisional applications did not carry the pressure responsive surfaces and did provide for a ball closure element having a diameter substantially equal to the outer diameter of the wireline retrievable valve housing in order to increase the flow area through the wireline retrievable valve.
Mott U.S. Pat. No. 3,858,650 discloses a dual controlled tubing retrievable housing without a flow controlling valve element for receiving and operating the through-the-flowline retrievable valve disclosed in U.S. Pat. No. 3,744,564 with either control line.